Liquid metal as a transformative material for flexible thermal cycling and point-of-care PCR

The increasing demand for decentralized pathogen detection has accelerated the development of miniaturized and flexible polymerase chain reaction (PCR) systems. While conventional reviews focus primarily on macro-to-micro structural downscaling, they rarely address two fundamental physical bottlenecks in tandem: the high thermal inertia of solid heaters and the extreme mechanical impedance mismatch at rigid-soft interfaces. This paper systematically reviews how gallium-based liquid metals (LMs) uniquely resolve these long-standing dilemmas by merging high metallic conductivity (∼3.4 × 10⁶ S/m) with intrinsic fluidity. We explore how these fluidic alloys achieve ultrafast thermal ramping rates exceeding 10 °C/s while maintaining stable operation under mechanical deformations beyond 100% strain, making them ideal for wearable and epidermal diagnostics. Key thermal actuation strategies-Joule, induction (>15 °C/s), and photothermal heating-are quantitatively evaluated alongside representative case studies of fully integrated, sample-to-answer modules. Finally, we identify critical engineering challenges in leakage control and power management, establishing a comprehensive roadmap for LM microfluidics to revolutionize personalized healthcare and mobile health monitoring.